Comparison of Density Estimation for CHAMP and GRACE Satellites

Abstract

This paper compares atmospheric density estimates obtained from precision orbit ephemerides (POE) for the CHAMP and GRACE satellites. GRACE-A and CHAMP POE data are used to derive atmospheric densities which are calibrated with densities derived from the onboard accelerometers of these satellites. The resulting calibrations are compared between the two satellites for many time periods at differing levels of solar and geomagnetic activity. An overall comparison of calibration for the two satellites is performed. In addition, three particular time periods are examined in greater detail for both satellites. Density is estimated as a correction to an existing baseline density model. The corrections to the Jacchia family of models are found to produce better calibration results with accelerometer data than the corrections to the MSIS family of models. The calibration for GRACE density estimation is found to be consistent regardless of solar and geomagnetic activity and matches the calibration for CHAMP density estimation during low activity times and differs only slightly during more active times.